Automatic voltage regulator



April 4, 1967 Q. J. MCCABE ETAL 3,312,891

i AUTOMATIC VOLTAGE REGULATOR Filed March-l2, 1963 Trag/Veys United States Patent Oiitice 3,312,891 AUTOMATIC VOLTAGE REGULATOR Owen J. McCabe and Raymond G. Edgerly, Jr., Bristol, Conn., assignors to The Superior Electric Company, Bristol, Conn., a corporation of Connecticut Filed Mar. 12, 1963, Ser. No. 264,552 4 Claims. (Cl. S23-43.5)

T'he present invention relates to an electric circuit that is connectible to a source of alternating current for producing an output voltage adjustable in va'lue and more particularly to such a circuit in which'the value to which the output voltage is adjusted is maintained substantially constant even with Wide variations in the value of the source voltagean-d the current control by the circuit.

VWhile it -has heretofore been proposed to provide a regulator that is capable of maintaining a substantially constant output voltage and for enabling the output volt age that is maintained constant to be adjusted, such devices have not been completely satisfactory. Normally, such proposed automatic volta-ge regulators have included regulating means connected to regulate the output voltage and have had an adjusting member that enables the changing of the value of the output voltage, with such a member being mechanically positioned in the regulating means in addition to being electrically connected therein. Also such heretofore known automatic voltage regulators have only provided for adjustment of the value of output voltage over a relatively small range of the value of input voltage and hence in many instances where it is desire-d to provide a value of output voltage that is only a small percentage ofthe source voltage, such devices have not been able to perform satisfactorily if at all.

It is accordingly an object of the present invention t-o Y provide an automatic voltage regulator which has an adjusting member and in which said adjusting member may be remotely positioned from the other components of the regulator and which requires only a minimum number of electrical connections therebetween.

Another object of the present invention is to provide in such an automatic voltage regulator for the selection of value of output voltage that is to be maintained constant to be over a wide range of the input voltage and thus enable selection of a value of output voltage that may be only a small percentage or a substantial percentage of the value of input voltage.

A further object of the present invention is to provide an automatic voltage regulator which achieves the above objects and yet is simple in construction, durable in Vuse `and maintains the value of output voltage substantially constant at its adjusted value.

Afeature of `the present invention resides in an auto` matic volta-ge regulator in which a regulating means is positioned between the input and output connections to regulate the output voltage. The regulating means which in the herein described embodiment is an adjustable voltage autotransformer that is mechanically actuated by a reversible motor has one channel which when energized causes the regulating means to increase t-he value of the output voltage while another channel when energized causes the regulating means to decrease the value of the output v-oltage. To control the energization of the channels, the present invention provides for having the output voltage to be continuously monitored and to produce a voltage which is related in value to the act-ual output voltage. In a-ddition a refe-rence circuit is employed to provide a substantially constant reference voltage. The voltages from the output vo-ltage sensing circuit and the reference circuit are algebraically added to produce the algebraio sum of the two voltages which thereby constitutes a signal that, when having one sense, serves to actuate 3,312,891 Patented Apr. 4, 1967 one channel of the regulator means while, if of the other sense, it serves to actuate the other channel of the motor. Moreover, to provide for adjusting the output voltage, the present invention has an adjusting member which selects only a portion of the reference voltage to be compared to the output voltage and by the selection of that portion of the reference voltage, the value of the output voltage which is desired to be maintained is thus achieved.

Particularly in the present invention the selection of the output voltage is achieved by the use of an adjusting member, specifically a potentiometer, which may be remotely positioned from the other components of the automatic voltage regulator circuit and need be connected thereto only by three wires. Additionally, by the circuit of the present invention, as it is an algebraic addition of voltages, the voltage loss in the connections to the potentiometer is minimized and hence the distance that the adjusting member is located from the regulator has little, if any, effect on its accuracy.

Other features and advantages will hereinafter appear.

In th-e drawing:

The only ligure is a schematic diagram of the adjustable voltage regulator of the present invention.

Referring to the drawing, the automatic volta-ge regulator of the present invention is generally indicated by the reference numeral 10 and includes a regulating means -which is specifically herein disclosed as an adjustable volt age autotransformer 11 having a winding 12 on which a tap 13 is movable to be in slidable electrical engagement therewith, as is well known in the art. The ends of the win-ding 12 are connected to a pair of input terminals 14 and 15 which in turn are connectible to a source of alternating current while th-e output of the autotransformer and hence the regulator appears between the terminal 14 and an output terminal 16 connected to the tap 13. Movement of the tap 13 on the winding 12 is controlled by an electric motor, generally indicated by the reference numeral 17 which is mechanically connected, as indicated by the dotted line 18, to eiTect movement of the tap 13.

The motor 17 is of a reversible type, such as disclosed in United States Patent No. 2,982,872, and includes a irst winding 19 and a second winding 20 with t-he windings having a common junction lead 21 connected t-o the terminal 15. A rst channel 22 connected to the iirst winding 19 for energizingv it with alternating current causes rotation of the motor in one direction and a second c-hannel 23 is connected to the second winding 20 to energize it to cause the motor to rotate in the other or reverse direction.

It will be appreciated that rotation of the motor by energization of the channel 22 serves to decrease the value Y output voltage to increase at these output terminals. The

first channel 22 is energized through a normally open relay switch 24 which through an RF choke 25 is connected by a lead 26 to the input terminal 14. Similarly, the channel 23 includes a normally open relay switch 27 also connected to the lead 26. Relay switch 24 is actuated by a relay coil 28 which upon energization closes the switch while the relay switch 27 is actuated by a relay coil 29 that also upon energization closes the switch 27. Closure of the switch 27 energizes the channel 23 and hence the second winding 20 across the input terminals 14 and 15 while closure of the switch 24 by energization of the relay coil 28 energizes the channel 22 and hence the first winding 19. For decreasing sparking and RF interference, chokes 30 and 31 and condensers 32 andv33 connected in the manner shown are provided.

The energization of the relay coils 28 and 29 is effected by a control circuit generally indicated by the reference 3 numeral 34 which includes gate contro-lled diodes, specifically herein, a first silicon controlled rectifier (SCR) 35 and a second SCR 36 though similar acting devices may be employed if desired. Each SCR is normally nonconducting in its anode-cathode path but upon a voltage signal appearing between a gate and cathode, it is triggered to lrender its anode to cathode path conducting. The relay coil 29 is energized upon conduction thro-ugh the SCR 35 with the relay coil 28 similarly energized upon the conduction through the SCR 36. In the embodiment of the invention disclosed, the relay coil 29 is connected between the vanode of the SCR 35 and a lead 37 while the relay 28 is connected between the anode of SCR 36 and the lead '37. The lead 37 is the positive side of a half-wave power supply, generally indicated by the reference numeral 38 that includes a secondary winding 39 of a transformer 40 having a primary winding 41 connected to the input terminals 14 and 15 and a one-way valve 42 in the lead 37. Thus the power supply 38 places across the anode-cathode of each SCR a half-wave unidirectional current by reason of a ground 43 connected to the other half of the secondary winding 39 and a ground 44 connected to the cathodes of the SCRs 35 and 36 through an anticipated network 45 that is more fully hereafter set forth.

The transformer 40 further provides a gate cathode bias supply for the SCRs, the circuit being indicated generally by the reference numeral 46 and includes a secondary winding 47, one-way valves 48 and 49, a filtering capacitor 50 and a breakdown or Zener diode 51 to- "gether with resistances 52 vand 53 connected in the manner shown. Moreover, there is provided a sensitivity potentiometer S4 connected through temperature compensating diodes 55 to the ground 43. The tap 56 of the potentiometer 54 is connected to a common junetion 57 between two similar resistances 58 and 59, each of which is connected through a lead 60 and 61 to the gates 62 and 63 of the SCRs 35k and 36 respectively. For filtering and to provide the proper voltages, condensers 64, 65, 66, 67 and resistances 68 and 69 together with reverse voltage gate protecting diodes 70 and 71 are interconnected between the leads 60 and 61 and the SCRs 35 and 36. It will be understood that adjustment of the potentiometer 54 serves to place between the gate and the cathode of each SCR a positive to negative bias voltage respectively having a value that is adjustable by the tap 56 thereof and thereby provides for controlling the sensitivity of the SCRs as will be hereinafter apparent.

The bias voltage between the gate and cathode of each SCR is insufficient in value to cause conduction of an 'SCR and hence energization of either the channel 22 or 23 is effected by impressing between the gates and cathodes a signal voltage which has one sense or polarity when it is desired to energize the channel 22 and an- 'other sense when it is desired to energize the channel 23. This signal voltage is derived from algebraically adding a voltage produced by an output voltage sensing circuit, 'generally indicated by the reference numeral 72 that produces a unidirectional voltage related to the value of the actual output voltage and a reference circuit indicated by the reference numeral 73 that produces a value of voltage which is constant but yet may be adjusted in value to set the value to which the output voltage is to be maintained.

Y Referring specifically to the output voltage sensing circuit 72, there is provided a transformer 74 having a primary winding 75 connected to the output terminals 14 and 16 and having a secondary winding 76, Whose output is rectified by a full-wave rectifier 77 connected in the manner shown. A resistance 78 is connected across the output of the rectifier 77 to thus have thereacross a voltage which is related to the actual output voltage. Preferably a filtering capacitor 79 and a resistor 80 are included; the latter may be adjustable if desiredto enable an initial setting of the circuit to compensate for tolerances inthe components.

The reference circuit 73 includes a winding 81 on the transformer 40 connected to a full-wave rectifier' 82 that produces a unidirectional current across a breakdown or Zener diode 83 connecte-d across the output of the ree4 tifiers. Additionally, a resistance 84 and filtering capacitor 85 are preferably provided.

In carrying out the present invention there is produced from the rectifiers across the breakdown diode a voltage sufficient to cause the diode to reversely conduct and hence produce a substantially constant voltage there'- across. A potentiometer 86 having a tap 87 is connected in parallel to the diode 83 with the tap being connected to the lead 61 and one end of the potentiometer to ari end of the resistance 78. The potentiometer 86 constitutes the adjusting member that enables selection of the value of the output voltage which is desired to'be maintained constant. It will be appreciated that only three connections are required to be made thereto and thus if it is positioned remotely from the other components of the automatic voltage regulator only three leads are required to maintain its functiona'bility in the regulator.`

With the above described components, in the operation of the regulator unidirectional voltagevexists across the resistance 78 between the points A and B and has a value which is related to the value of the actual output voltage while a unidirectional voltage exists betweenthe points' C and D which has avalue that is substantially constant as determined by the breakdown or avalanche voltage of the diode 83. The lead 60 is connected to 'the pdint B and the had 61 to the tap e7; 11 will be'ppreciated that if the voltage between the points A and B is 'c'jual to the voltage between the point C and tap 87 there is nd signal produced in the leads 60 and 61 which would cause conduction of the SCRs 35 and 36. If howve the voltage between the points A and B is higher than that between D and tap 87, which indicates that it is necessary for the channel 22 to be energized to effect a decrease in the output voltage, then a relatively positive signal appears at the tap 87 as .compared to the voltage at point B, even though both the tap 87 and point B have nega= tive voltages with respect to thepositive voltages atthe points A and D. When this signal has voltage value when added to the bias voltage, it causes conduction of the SCR 36 and consequent energization of the channel 221 On the other hand, if the voltage between the pints A and B is less than the voltage between the point and the tap 87 then the voltage at the point B is positive with respect to the voltage at the tap 817, indicating that the ouput voltage is lower ythan that desired, and thus the SCR 35 is caused to be conducting to energize the channel 23 by the positive signal appearing in the lead 601 It will be appreciated that with the structure of the automatic voltage regulator as heretofore vset forth and particularly the algebraic -adding of the voltage, that it is'` possible to provide an output voltage which may be selected to be as little as 2 or 3% of the input voltage and to maintain this output voltage constant. Moreover, as voltages are compared, there is little, if any, current to the potentiometer 86 which, if it were remotely positioned, prevents the introduction of error by minimizing the voltage drop in the connections thereto. The voltage across the breakdown diode 83 and hence across the potentiometer 86 has a maximum value which is at least equal to the value of voltage that is produced between the points A and B for the maximum value of output voltage. It will be appreciated that even at a very low setting value of output voltage, a positive signal sufficient to trigger an SCR is produced by reason of the algebraic sum of the two voltages.

The anticipation network 45 is connected as shown between the cathodes of the SCRs 35 and 36 and the ground 44. It consists of a diode 88 and an RC network composed of capacitor 89 and resistor 90 with three elements being connected in parallel. Normally, without conduction `through the SCRs there is placed between the anode and cathode of the SCRs the voltage appearing between the leads 37 and ground 43. However, upon conduction therethrough the voltage therebetween is decreased by the forward dropthrough the diode 88 which in effect decreases the value of the negative ground with respect to the gate to thereby decrease the bias between the gate and cathode of each SCR and thus increase the value of the positive signal between the point B and tap 87 needed to maintain the SCR conducting. As the actual output voltage approaches that determined by the setting of the potentiometer S6, the voltage across the gate and cathode of the conducting SCR decreases below the value necessary to maintain the SCRs conducting by the positive signal and thus it ceases its conduction before the value of the signal is such that without the network 45 it would normally render the SCRs conducting. -Upon cessation of conduction through the SCR, the network 45 is in effect out of the circuit but if the positive signal is of sufficient value it may Aagain initiate further conduction of the SCR yand consequent intermittent energization of the channel. The voltage drop caused by the diode 88 however is preferably selected so that it will cease the conduction through an SCR and effect deenergization of its associated channel to substantially accommodate for the momentum in the regulating means that exists after dcenergization of the channel and hence the regulating means will after deenergization coast sufiiciently to change the output voltage an amount that will compensate for the voltage drop caused by the diode 88.

The RC network elements 89 and 90 not only serve to maintain the closure of the relays 28 or 29 during the half cycle when there is no power through an SCR but also primarily function to limit the rate of decrease of the voltage drop across the diode S8 during this nonconducting lhalf cycle.

It will accordingly be rappreciated that there has been disclosed an automatic voltage regulator that provides an output voltage whose value may be selected from a range that extends from a minimum of substantially zero to a maximum of at least as large as the input voltage. The adjusting of the output voltage within this range is moreover capable of being efectuated from a location that is remote from the regulator by positioning at the remote location an adjusting member which has specifically heretofore been disclosed as an adjustable potentiometer. By reason of the structure of the regulator only a minimum number of wires or connections are required between the remotely located adjusting member and the other components of the regulator and in addition the distance therebetween fails to introduce any substantial error into the vregulator because of the minimizing of the effect of voltage losses in the connections.

Variations and modifications may -be made within the scope of the claimsV and portions of the improvements maybe used without others.

We claim: Y

1. An automatic voltage regulator for providing and maintaining an adjustable A.C. voltage comprising input means connectible to a source of alternating current, output means whereat the output voltage appears, regulating means connected between the input and output means for regulating tfhe value of output voltage and including a first channel means which upon energization increases the v-alue of output voltage and a second channel means which upon -actuation decreases the value of the output voltage, means connectible -to the output means for providing a unidirectional current-having a voltage value related to the value of the output voltage, means connectible to a source of electrical energy for providing another unidirectional current having a substantially constant voltage value and including a breakdown diode having a Value of avalanche voltage at least equal to the maximum value of the 4unidirectional voltage for the maximum value of output Voltage, adjustable means for selecting a set value of the another unidirectional current, means v for algebraically adding the unidirectional current and the set value of the another unidirectional current to produce an algebraic sum signal, and means for receiving the signal and causing energization of the first channel when the signal is of one sense and for causing energzation of the second channel when the signal is of the opposite sense.

2,. An automatic voltage regulator for providing and maintaining an adjustable A.C. voltage comprising input means connectible to a source of alternating current, output means Whereat the output voltage appears, regulating means connected between the input and output means for regulating the value of output voltage and including la rst channel means which upon energization increases the value of output voltage and a second channel means which upon actuation decreases the value of the output voltage, means connectible to the output means for providing a Iunidirectional current having a voltage value related to the value of the output Voltage, means connectible to 1a source of electrical energy for providing another unidirectional current having a substantially constant voltage value, adjustable means for selecting a set value of the another unidirectional current, means for algebraically adding the unidirectional current -and the set value of the another unidirectional current to produce an algebraic sum signal, and means for receiving the signal :and causing energization of the first channel lwhen the signal is of one sense and for causing energization of the second channel when the signal is of the opposite sense, said lastnamed means including a controlled rectifier having an anode, cathode and gate connected in each channel with the signal being impressed between the gates and cathodes, means for supplying a bias potential between the cathode and gate and means for decreasing the bias potential only when a controlled rectifier is conducting through its anode and cathode.

3. An automatic voltage regulator for providing and maintaining an adjustable A.C. voltage comprising i-nput means connectible to a source of alternating current, output means whereat the output voltage appears, regulating means connected between the input and output means for regulating the value of output voltage and including a first channel means which upon energization increases the value of output voltage and a second channel means which upon actuation decreases the value of the output voltage, means connectible to the -output means for pro viding a unidirectional current having a voltage value related to the value of the output voltage, means connectible to a source of electrical energy for providing another unidirectional current having a substantially constant voltage Value and including a breakdown diode having a value of avalanche Voltage at least equal to the maximum value of the unidirectional voltage for the maximum value of output voltage, adjustable means for selecting a set value of the another unidirectional current and including a settable member havin-g a range from substantially zero to a value at least equal to the maximumvalue of the unidirectional voltage for the maximum value of output voltage, means for algebraically ading the unidirectional current and the set value of the another unidirectional current to produce an algebraic sum signal, and means for receiving the signal and causing energization of the first channel when the signal is of one sense and for causing energization of the second channel when the signal is of the opposite sense, said last-named means including a controlled rectifier having an anode, cathode and gate connected lin each channel with the signal being impressed between the gates and cathodes, means for supplying a `bias potential between the cathode and gate and means for decreasing the bias potential only when a controlled rectifier is conducting through its anode and cathode.

4. An automatic voltage regulator comprising an adproducing a unidirectional voltage proportional to the lo output voltage and including a step-down transformer having a primary winding connected to the output of the autotransformer, a secondary winding and rectifying means connected to the secondary winding; reference means for producing a substantially constant another unidirectional Voltage and including a step-down transformer winding connectible to the source of alternating current, -a secondary winding, rectifying means connected to said secondary winding, a breakdown diode having a value of avalanche voltage at least equal to the maximum value ofthe unidirectional voltage for the maximum value of output voltage produced by the proportional means and -a settable member connected to provide a range of another yunidirectional voltage from substantially zero to a value at least equal to the maximum value of the unidirectional voltage for the maximum value of output voltage; 4comparing means for comparing the two voltages inclu-ding connections placing the two voltages in opposition to produce a signal in the connections indicating the higher voltage and the magnitude of the difference between the two voltages; and means responsive to the signal of the comparing means for energizing the one channel if one voltage is higher or the other channel if the other voltage is higher to thereby alter the output voltage to a value that substantially reduces the difference between the two volt-ages, said last-named means including a controlled rectier having an anode, cathode :and gate connected in each channel with the signal being impressed between the gates and cathodes, means for supplying a bias potential between the cathode and gate vand means for decreasing the bias potential only when a controlled rectifier is conducting through its anode and cathode.

References Cited by the Examiner UNITED STATES PATENTS 2,619,630 11/1952 Stone 323-46 3,026,470 3/1962 Webb 323-435 3,123,762 3/1964 Throop 323-22 3,123,763 3/1964 Kettler 323-22 3,129,380 4/2964 Liohowsky 323-45 3,202,903 8/1965 Ribbs S23-43.5 3,252,078 5/1966 Conner 323-435 JOHN F. COUCH, Primary Examiner.

LLOYD MCCOLLUM, Examiner.

W. E. RAY, S. W. WEINBERG, Assistant Examiners. 

1. AN AUTOMATIC VOLTAGE REGULATOR FOR PROVIDING AND MAINTAINING AN ADJUSTABLE A.C. VOLTAGE COMPRISING INPUT MEANS CONNECTIBLE TO A SOURCE OF ALTERNATING CURRENT, OUTPUT MEANS WHEREAT THE OUTPUT VOLTAGE APPEARS, REGULATING MEANS CONNECTED BETWEEN THE INPUT AND OUTPUT MEANS FOR REGULATING THE VALUE OF OUTPUT VOLTAGE AND INCLUDING A FIRST CHANNEL MEANS WHICH UPON ENERGIZATION INCREASES THE VALUE OF OUTPUT VOLTAGE AND A SECOND CHANNEL MEANS WHICH UPON ACTUATION DECREASES THE VALUE OF THE OUTPUT VOLTAGE, MEANS CONNECTIBLE TO THE OUTPUT MEANS FOR PROVIDING A UNIDIRECTIONAL CURRENT HAVING A VOLTAGE VALUE RELATED TO THE VALUE OF THE OUTPUT VOLTAGE, MEANS CONNECTIBLE TO A SOURCE OF ELECTRICAL ENERGY FOR PROVIDING ANOTHER UNIDIRECTIONAL CURRENT HAVING A SUBSTANTIALLY CONSTANT VOLTAGE VALUE AND INCLUDING A BREAKDOWN DIODE HAVING A VALUE OF AVALANCHE VOLTAGE AT LEAST EQUAL TO THE MAXIMUM VALUE OF THE UNIDIRECTIONAL VOLTAGE FOR THE MAXIMUM VALUE OF OUTPUT VOLTAGE, ADJUSTABLE MEANS FOR SELECTING A SET VALUE OF THE ANOTHER UNIDIRECTIONAL CURRENT, MEANS FOR ALGEBRAICALLY ADDING THE UNIDIRECTIONAL CURRENT AND THE SET VALUE OF THE ANOTHER UNIDIRECTIONAL CURRENT TO PRODUCE AN ALGEBRAIC SUM SIGNAL, AND MEANS FOR RECEIVING THE SIGNAL AND CAUSING ENERGIZATION OF THE FIRST CHANNEL WHEN 